So, I've recently branched off into singing. I've been working on it over the last year or so.

Anyway, I have myself a dilema. I sing a lot of hard rock. Now, I can either sing with relatively good pitch in a rather dull way or I can really get into the music, but I tend to make more mistakes.

In terms of performing, whats the better choice?
"This nightmare's gonna break me.
Please, Daylight, save me..."
train your ear and your voice. once you have it at a functional level, you can really get into it.

think of it from the perspective of an instrument. if you were putting on a show, would you rather bang at the piano or hit the right notes?
Anfangen ist leicht, Beharren eine Kunst.
And this is why autotune is so popular.

You're best off getting a solid foundation with proper technique and hitting the notes and working on your ear. After that, you can branch out and push yourself and go a little more crazy. Make sure you have the fundamentals down though, you don't want to start any bad habits by rushing the learning process.
Hey OP,
I had this issue when I first started as well. So I got lessons and practiced with a keyboard. For the bands first demo, I didn't go all out and instead made sure I wrote something that sounded decent but was also well within my limits. Now after countless shows and practice, my ear is ready for the bigger leagues and thus far have written much more emotional tunes. 6 months ago I would not have been ready for this.

Fact is, nobody wants to hear your silly arse go off key often. Most folks focus on the vocalist and this is the best way to instantly lose people interest or worse give them a bad feeling about you.